Horton

Re: PATCH: logical_work_mem and logical streaming of large in-progress transactions

Tomas Vondra <tomas.vondra@2ndquadrant.com>

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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, Michael Paquier <michael@paquier.xyz>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2020-03-29T15:31:05Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Tighten the concurrent abort check during decoding.

  2. Improve hash_create()'s API for some added robustness.

  3. Use HASH_BLOBS for xidhash.

  4. Fix initialization of RelationSyncEntry for streaming transactions.

  5. Remove unused function declaration in logicalproto.h.

  6. Add additional tests to test streaming of in-progress transactions.

  7. Fix inline marking introduced in commit 464824323e.

  8. Add support for streaming to built-in logical replication.

  9. Fix the SharedFileSetUnregister API.

  10. Fix comment in procarray.c

  11. Suppress compiler warning in non-cassert builds.

  12. Extend the BufFile interface.

  13. Mark a few logical decoding related variables with PGDLLIMPORT.

  14. Implement streaming mode in ReorderBuffer.

  15. Extend the logical decoding output plugin API with stream methods.

  16. WAL Log invalidations at command end with wal_level=logical.

  17. Immediately WAL-log subtransaction and top-level XID association.

  18. Allow logical replication to transfer data in binary format.

  19. Only superuser can set sslcert/sslkey in postgres_fdw user mappings

  20. Track statistics for spilling of changes from ReorderBuffer.

  21. Add logical_decoding_work_mem to limit ReorderBuffer memory usage.

  22. logical decoding: process ASSIGNMENT during snapshot build

  23. Emit invalidations to standby for transactions without xid.

On Sun, Mar 29, 2020 at 11:19:21AM +0530, Amit Kapila wrote:
>On Sun, Mar 29, 2020 at 6:29 AM Tomas Vondra
><tomas.vondra@2ndquadrant.com> wrote:
>>
>> On Sat, Mar 28, 2020 at 03:29:34PM +0530, Amit Kapila wrote:
>> >On Sat, Mar 28, 2020 at 2:19 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>> >
>> >How about if instead of writing an XLOG_XACT_ASSIGNMENT WAL, we set a
>> >flag in TransactionStateData and then log that as special information
>> >whenever we write next WAL record for a new subtransaction?  Then
>> >during recovery, we can only call ProcArrayApplyXidAssignment when we
>> >find that special flag is set in a WAL record.  One idea could be to
>> >use a flag bit in XLogRecord.xl_info.  If that is feasible then the
>> >solution can work as it is now, without any overhead or change in the
>> >way we maintain KnownAssignedXids.
>> >
>>
>> Ummm, how is that different from what the patch is doing now? I mean, we
>> only write the top-level XID for the first WAL record in each subxact,
>> right? Or what would be the difference with your approach?
>>
>
>We have to do what the patch is currently doing and additionally, we
>will set this flag after PGPROC_MAX_CACHED_SUBXIDS which would allow
>us to call ProcArrayApplyXidAssignment during WAL replay only after
>PGPROC_MAX_CACHED_SUBXIDS number of subxacts.  It will help us in
>clearing the KnownAssignedXids at the same time as we do now, so no
>additional performance overhead.
>

Hmmm. So we'd still log assignment twice? Or would we keep just the
immediate assignments (embedded into xlog records), and cache the
subxids on the replica somehow?


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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